Code
P0264
HUMMER
P — Powertrain
Cylinder 2 Injector Circuit Low
AI status
Completed
Completed
100%
Causes
- Open or shorted wiring in injector circuit (short to ground)
- Corroded, loose, damaged or contaminated injector connector
- Faulty fuel injector (stuck open/shorted coil)
- Poor or missing circuit power/ignition feed or blown fuse/relay
- Poor ground connection for injector circuit or engine ground strap
- Faulty ECM/PCM injector driver or internal electronic failure
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated (check engine light)
- Rough idle or misfire localized to cylinder 2
- Poor engine performance, hesitation, or reduced power
- Hard starting or increased cranking time
- Increased fuel consumption and possible exhaust smell or smoke
- Occasional stalling or limp-home behavior depending on severity
What to check
- Retrieve freeze frame and scan data; note related codes (misfires, low battery voltage, communication faults)
- Perform a visual inspection of injector connector, wiring harness, and nearby grounds for corrosion, melted insulation, or damage
- Check battery voltage and charging system; verify proper supply voltage to injector rail/fuse/relay
- Backprobe cylinder 2 injector connector with key ON and with engine cranking/running to observe voltages
- Measure injector coil resistance with the connector disconnected and compare to service specifications
- Wiggle test wiring while engine is running to try to reproduce the fault
Signal parameters
- Key ON, engine OFF: injector supply (reference) should be near battery voltage at the connector (typically ~12 V)
- When energized: driver typically pulls the injector circuit toward ground in pulses; measured as voltage pulses between ~0 V and battery voltage
- Pulse width varies with load/engine speed (roughly 1–10 ms for many conditions) — consult vehicle service manual for exact pulse widths
- Injector coil resistance varies by injector type — consult service manual; if unknown, typical ranges can be ~2–20 ohms (low-impedance) or 12–20+ ohms (high-impedance). Verify with manufacturer specs
- Continuity from injector connector to ECM should be low (near 0 ohms) and no short to ground when injector disconnected
Diagnostic algorithm
- Confirm trouble code and note freeze-frame / freeze data. Clear codes and see if P0264 returns.
- Check battery voltage and charging system; ensure stable supply (≥12 V) during cranking and running.
- Visually inspect cylinder 2 injector connector, wiring harness, and engine grounds for damage, corrosion, melted insulation, or loose pins.
- With key ON (engine OFF) backprobe injector connector: verify reference/supply voltage is present (battery voltage).
- Start engine or crank while backprobing: observe injector driver signal with a voltmeter or preferably an oscilloscope. Look for regular pulsed signal; note if voltage stays low or is missing.
- With ignition OFF remove injector harness and measure injector coil resistance with an ohmmeter; compare to spec. If coil is shorted (very low ohms) or open, replace injector.
- If injector resistance is normal but the driver signal is low or absent, perform continuity check between injector connector and ECM driver pin. Repair any opens/shorts. Check for short-to-ground on driver circuit.
- Swap injector from cylinder 2 with another cylinder (same type) and run the engine. If code/misfire follows the injector, replace the injector. If it stays on cylinder 2, suspect wiring or ECM driver.
- Inspect and test fuses/relays and power feed for injector circuits. Repair or replace as needed.
- If wiring and injector check out, test or replace ECM/PCM or ECM connector as last resort following manufacturer procedures.
- After repairs, clear codes and perform a road test; verify no return of P0264 and that engine runs normally.
Likely causes
- Damaged connector pins at cylinder 2 injector
- Short to ground in the injector harness near the injector or in the loom
- Failed injector coil (low resistance or internal short)
- Faulty or weak battery/ignition supply or blown/insecure fuse/relay feeding injectors
- Damaged wire insulation where it contacts chassis or hot engine component
Fault status
Status
P0264 — Cylinder 2 Injector Circuit Low: low voltage or short to ground detected on injector control circuit for cylinder 2; MIL set.
Repair difficulty: Medium
Diagnostic time: 1–3 hours
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